lib/libc/syslog/lib_syslog.c : fix dbg and printf log mixup

Use semaphore on stdout file stream, so that the entire dbg log is pushed to output
thus stopping the log mixup due to context switching.

PRINTING FROM THREAD
hello_main: printing from main
PRINTING FROM THREAD
hello_main: printing from main
PRINTING FROM THREAD
hello_main: printing from main
PRINTING FROM THREAD
hello_main: printing from main

lib/libc/syslog/lib_syslog.c

@@ -58,13 +58,16 @@
 
 #include <stdio.h>
 #include <syslog.h>
-
+#include <tinyara/arch.h>
 #include <tinyara/clock.h>
 #include <tinyara/streams.h>
 #if defined(CONFIG_LOGM) && defined(CONFIG_SYSLOG2LOGM)
 #include <tinyara/logm.h>
 #endif
 #include "syslog/syslog.h"
+#if CONFIG_NFILE_STREAMS > 0
+#include "lib_internal.h"
+#endif
 
 /****************************************************************************
  * Pre-processor Definitions
@@ -121,9 +124,10 @@ static inline int vsyslog_internal(FAR const char *fmt, va_list ap)
 	struct lib_outstream_s stream;
 #endif
 
+	int ret;
+
 #if defined(CONFIG_SYSLOG_TIMESTAMP)
 	struct timespec ts;
-	int ret;
 
 	/* Get the current time */
 
@@ -154,15 +158,31 @@ static inline int vsyslog_internal(FAR const char *fmt, va_list ap)
 
 	lib_rawoutstream(&stream, 1);
 
+#if CONFIG_NFILE_STREAMS > 0 && (defined(CONFIG_BUILD_FLAT) || defined(__KERNEL__))
+	if(!up_interrupt_context() && getpid() != 0){
+		lib_take_semaphore(stdout);
+	}
+#elif CONFIG_NFILE_STREAMS > 0
+	lib_take_semaphore(stdout);
+#endif
+
 #if defined(CONFIG_SYSLOG_TIMESTAMP)
 	/* Pre-pend the message with the current time */
 
 	if (ret == OK) {
 		(void)lib_sprintf((FAR struct lib_outstream_s *)&stream, "[%6d.%06d]", ts.tv_sec, ts.tv_nsec / 1000);
 	}
 #endif
-
-	return lib_vsprintf(&stream.public, fmt, ap);
+	ret = lib_vsprintf(&stream.public,fmt,ap);
+
+#if CONFIG_NFILE_STREAMS > 0 && (defined(CONFIG_BUILD_FLAT) || defined(__KERNEL__))
+        if(!up_interrupt_context() && getpid() != 0){
+                lib_give_semaphore(stdout);
+        }
+#elif CONFIG_NFILE_STREAMS > 0
+	lib_give_semaphore(stdout);
+#endif
+	return ret;
 
 #elif defined(CONFIG_ARCH_LOWPUTC)
 	/* Wrap the low-level output in a stream object and let lib_vsprintf